Add Dynu Terraform brownfield DNS documentation layer

docs/infrastructure-inventory.md

@@ -50,6 +50,12 @@ Compose files define intended service runtime composition, networking, labels, a
 
 Dynu write operations are intentionally blocked in this repository stage.
 
+### 7) Terraform Dynu DNS layer
+
+`infrastructure/terraform/dynu/` is the brownfield Terraform DNS mirror/reconciliation root for Dynu domain/record inventory outputs.
+
+At this stage it is primarily documentation-oriented catalog output, ready for one-object-at-a-time imports.
+
 ## Output shaping expectations
 
 When adding Terraform outputs for documentation/tooling: